Local multipoint distribution systems (LMDS) are RF cellular data communication systems which augment or replace wired land-line telecommunications available to stationary subscribers. Typically, an LMDS operates in or near the K.sub.a band where a wide portion of the electromagnetic spectrum may be dedicated for exclusive use by the LMDS. This wide bandwidth allows LMDS subscribers to communicate data at much higher data rates than may be currently accommodated through wired land-line connections. An LMDS need not entirely replace the public switched telecommunications network (PSTN). Rather, an LMDS may couple to a PSTN and use the PSTN to trunk bulk communications. Desirably, an LMDS replaces or augments the final wiring links between a central office and subscribers' premisses much like conventional cellular communication systems use RF communications as a final link to cellular radiotelephone subscriber units.
However conventional LMDS systems use their allocated spectrum inefficiently. A typical LMDS has an architecture similar to architectures used in conventional cellular technology. Accordingly, spectrum reuse is limited, data rates are either inflexible from user to user and call to call or minimally alterable, and the system is not efficiently configured to accommodate a stationary subscriber population. Limited spectrum reuse is undesirable because the overall amount of call traffic which can be carried by the LMDS spectrum in a given area is likewise limited. A mobile subscriber-population architecture rather than a stationary subscriber-population architecture leads to inefficient spectrum usage. For example, when a portion of the LMDS spectrum is consumed in overhead communications to resolve Doppler and insure that acceptable signal levels exist throughout an entire cell, such spectrum is not available for subscriber data traffic.
A highly undesirable feature of a conventional LMDS is an inability to efficiently support a wide variation in data rates to different subscriber units. Conventional cellular systems predominantly permit data rates consistent with voice communication. While some telecommunication systems permit subscriber communication at higher and lower data rates, the higher data rates are not sufficiently different from the lower data rates to provide significant advantages, and few subscribers actually take advantage of the modestly higher data rates. Consequently, inefficiencies pose no serious problems. However, the wide bandwidths supported by an LMDS can be vastly higher than low data rates which are consistent with voice communication, and a majority of subscribers subscribe to an LMDS to have the vastly higher data rates. Consequently, a need exists for an LMDS that efficiently accommodates a wide range of data rates for different subscribers.